An increasing number of lawyers are representing defendants who decide not to roll over and settle out of court when the Recording Industry Association of America (RIAA) sues them for illegal downloading.

The lawyers are questioning the basic merit of the lawsuits filed by the music industry trade body against individual file swappers.

The RIAA has filed 15,500 lawsuits against illegal downloaders, 25 per cent of whom have settled out of court.

New York defence lawyer Ray Beckerman told Variety magazine: "All the RIAA knows is that someone on a computer located somewhere had a file-sharing folder that had copyrighted songs in it. 

"They do not know whether the songs were obtained illegally, and they do not even know whether the person they're suing is the person who set up the file-sharing account. Most [defendants] did not."

The RIAA, however, remains confident in its investigative methods and will continue its strategy of hunting down individuals.

Beckerman believes that many defendants are simply intimidated into settling out of court. "Litigation could cost as much as $100,000, and the RIAA is saying that this will 'all go away if you pay us maybe $4,000'."

An intellectual property lawyer added: "When you see grandfathers getting sued, it's a function of an overly broad net which the industry has cast.

"There is no doubt that these suits are being brought for effect, and one way to increase effect is to drag in hundreds of people in one shot. But then you've got to question whether enough due diligence is being done."